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Haloarenes (e.g., chlorobenzene) are much less reactive than haloalkanes toward nucleophilic substitution because of all the following EXCEPT:
AResonance — the C–X bond acquires partial double-bond character
BHalogens are more electronegative in haloarenes than in haloalkanes
CInstability of the phenyl cation rules out SN1
DC–X carbon is sp² hybridised (more s-character) → shorter, stronger C–X bond than in haloalkane (sp³)
Answer & Solution
Correct answer: B. Halogens are more electronegative in haloarenes than in haloalkanes
Reasons haloarenes resist nucleophilic substitution: (i) **resonance** delocalises X lone pair into the ring → partial C=X character; (ii) **sp² C is more electronegative** → shorter, stronger C-X bond; (iii) **phenyl cation is very unstable** → SN1 ruled out; (iv) electron-rich nucleophile repelled by electron-rich aromatic ring. Halogen electronegativity itself is similar — **D is the wrong choice**.
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